Viewing optical systems provided with holograms are well known. A hologram may be used as a condenser lens to match the pupil of the eyepiece with the objective system (Japanese Laid-Open Patent Application No. SHO 51-19530), and also may be used as an information display. For example, the viewing optical systems disclosed in Japanese Published Patent No. 58-27504 and Japanese Laid-Open Patent Application No. 59-185319 are provided with a hologram of a pre-recorded specific display pattern, and this pre-recorded display pattern is regenerated and displayed together with a photographic subject image.
In these viewing optical systems, only the specific display pattern recorded when the hologram was generated can be displayed and optional information not recorded in the hologram cannot be displayed.